Burst communication receiving system based on DSSS-OQPSK

Abstract

The invention discloses a burst communication receiving system based on DSSS-OQPSK. The burst communication receiving system comprises a radio frequency front-end module, a signal capturing module, alocal carrier generation module, a carrier tracking module, a coherent demodulation module, a local spreading code generation module, a correlation peak capturing module, a code tracking module and ade-spreading module, wherein the signal capturing module sequentially performs quartic operation and high-pass filtering on the digital intermediate frequency OQPSK signal, then completes coarse capture of a burst signal through Fourier transform, estimates frequency offset of a transmitting end and a receiving end, and performs coarse correction on a generated local carrier in real time; and thecarrier tracking module completes carrier tracking by adopting an improved Costas ring oriented to a decision ring according to decision-oriented carrier phase estimation, and completes frequency offset correction. According to the method, the frequency error is controlled within a very small range, so that the capture bandwidth and the locking time of tracking the phase-locked loop are reduced, and the system performance index is improved.

Description

technical field [0001] The invention belongs to the technical field of communication systems, in particular to a burst communication receiving system based on DSSS-OQPSK. Background technique [0002] In a DSSS (Spread Spectrum) system, in order to correctly restore user information, it is necessary to synchronize a spreading code for despreading generated at a receiving end with a spreading code at a transmitting end. Spread spectrum code synchronization is generally divided into two steps: the first step is to search and capture the initial phase of the spread spectrum code, so that the code phase error with the transmitter is less than 1 bit, which can ensure that the despread signal passes through the narrowband behind the correlator IF filter, this is the acquisition process; the second step is to further reduce the code phase error on the basis of the initial synchronization, so that the established synchronization can be maintained, this is the code tracking process. ...

AI Technical Summary

Problems solved by technology

However, there is a problem with using a phase-locked loop for frequency offset correction. When the frequency offset is relatively large, the capture bandwidth of the phase-locked loop must be large, which will increase the loop locking time and reduce the loop stability.

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